Grinding wheel



v Nov; 14, 1933.v J TONE ET AL GRINDING WHEEL Filed Feb. 2, 192a.

INVENTOR3 Ill/l1 Patented Nov. 14, Q 1933 UNITED STATES PATENT {OFFICE GRINDING Application February 2, 1928. Serial No. 251,281

' 1o (oi. 5l--2ll'i) invention relates to grinding wheels, and more particularly to grinding wheels having expansion Joints to permit unequal thermal expansion between the parts. The invention is illustrated as embodied in a segmental grinding wheel of the type used for grinding wood pulp,

- in which a number of segmental blocks of abrasive material are mounted on a metallic hub or drum. The hub or drum is preferably provided 3 with keys. which interlock with keyways in the abrasive blocks so as to positively lock them againts centrifugal movement. These wheels may be several feet in diameter. They are subjected to considerable variations in temperature from & that of zero winter weather to that of boiling water. The metal oi'the hub or drum has about double the thermal coemcient of expansion of the abrasive material, so that changes in temperature tend to cause relative movement between the metallic part and the abrasive part of the wheel.

Also, when the wheel is used, different parts may become unequally heated, tending to produce difierent degrees of expansion in different parts of the wheel.

The unequal expansion, particularly between the metal and the abrasive parts of the wheel, and also between the different parts of the abrasive structure, is compensated for by expansion joints. These expansion joints are preferably formed as 39 illustrated herein by an elastic material which is incorporated in the cement joint uniting the parts, although the expansion joint might be otherwise formed.

In the accompanying drawing, the invention is illustrated as applied to a segmental pulp grinding wheel, but it isto be understood that the in-' vention may be otherwise embodied within the scope of the claims.

In the illustrated embodiment of the inven- 40 tion: I

Figure 1 is an end elevation of thedrum and grinding wheel segments looking in the direction of the axis of the drum;

Figure 2 is a partial view of the developed peripheral surface of the grinding segments as assembled and the joints therebetween; and

Figure 3 is an enlarged sectional view through a portion of the grinding wheel showing the drum and assembled segments and the Joints therebe-. 5o tween.

Referring to the drawing, reference numeral 2 designates generally an abrasive wheel mounted upon a shaft 3. The wheel comprises a metallic drum or hub 4 having wedge-shaped ribs 5, dlsposed longitudinally along its outer peripheral surface. The segmental blocks 6 of abrasive material are carried on the hub or drum and are locked thereon against centrifugal movement by the wedge-shaped keys or ribs 5. The blocks 6 may be of any suitable material, such. as bonded 80 silicon carbide, bonded aluminous abrasive, or natural abrasive stone. The blocks are provided with undercut extensions 7, adapted to interlock with the keys 5, whereby the abrasive blocks are positively keyed or locked to the metallic drum.

Expansion joints are provided between the metal drum and the abrasive blocks, and also preferably between the abrasive blocks themselves. The expansion joints are preferably made up of a cement and an elastic material, such as paper.

As illustrated in the drawing, the expansion joint between the metallic drum and the abrasive blocks is formed by a layer of paper 8 which islaid along the surface of the drum and around the keys 5, over which is applied a layer of cement 9 to fill up the remaining space between the paper and the abrasive blocks. The expansion joint between the blocks themselves is formed of a layer of paper 10, preferably corrugated, as shown, which is embedded in cement 11.

The elastic material used for forming the expansion joints may be paper, press board, fibre board, hard rubber, or any other suitable yielding material. We prefer to use a tough vegetable fibre paper or board, waterproofed or chemically treated to resist penetration of liquids, and about 3 5d of an inch thick. We have found that a suitable expansion joint may be made by using a water-resistant paper known to. the trade as Oilpac. This is a tough vegetable iibre chemically treated to resist the penetration of liquids and to withstand temperatures up to about 300 F. The paper is preferably smooth as laid against the metal and over the keys, and is preferably corrugated as used between the blocks. as this assists in the pouringand uniform distribution of the cement.

Any suitable cement may be used for filling up the space between the blocks and the metal, and between the blocks themselves. Melted sulphur is an example of a cement which may be used, since it can be poured in and hardens in place. We have used a sulphur compound known to the trade as Lavasul cement, which is-coinposed of 95% sulphur and about 5% finely ground coke. This cement may be melted and poured like sulphur.

Abrasive wheels of the character illustrated are usually assembled at a temperature of about 175 F. The wheels, of course, are afterwards subjected to cold which may be in the neighborhood of zero under winter shipping conditions. The metallic drum under reduced temperature contracts more than the abrasive, so that the drum tends to pull away from the surrounding ring of abrasive blocks. I

lhe keys 5 and the extensions 7 form a positive interlock between the metal and the abrasive. If the joints between the metal and the abrasive were filled with an unyielding joint material, the greater contractionof the metallic drum under cold would tend to pull off the undercut extensions l and rupture the abrasive blocks. The expansion joints, however, provide for the relative difierence in thermal contraction and expansion between the metallic drum and the ring of abrasive segments which is interlocked therewith. When the abrasive wheel is heated up, as for exple, in the grinding of pulp when the wheel may operate at the temperature of boiling water, the expansion joints allow for the relative difierence of. expansion of the metallic and abrasive parts of the wheel. The expansion joints also allow for difierence in the thermal expansion of unequally heated portions of the abrasive surface oi the wheel.

In building the wheel, the thickness of the paper is calculated to compensate for the contraction of the metallic drum from a temperature of about 175 l t, at which the wheel is assembled, to a temperature of 30 F., to which the wheel may be subjected in winter.

This insures the wheel against the fracture of the abrasive segments. due to the thermal contraction of the drum. The thickness of paper sumcient to provide for this is found to be sufiicient to provide for the thermal changes to which the wheel is subjected in grinding pulp.

The expansion joints also serve as a safeguard against strains which may be put upon the wheel, due to the increase in size of the locking keys 5 by rusting or oxidation.

The composite expansion joint formed of a layer oi resilient material such as a sheet of fibrous material or paper, and a readily pourable cementitious filling material, has great practical advantages in assembling a grinding wheel, particularly a pulp wheel. The wheel may be as sembled with the sheets of paper in the joints and beiore the cementitious filling materialis applied. This permits the parts to be readily and very accurately spaced. After the wheel is so assembled the cementitious filling material may be then poured into the narrow interstices or crevices between the blocks and the drum and between the blocks themselves, such crevices being usually in the neighborhood of about of an inch wide. A. cementitious filling material such as sulphur or "Lavasul may be melted to a readily pourable mobile fluid condition, in which it can be readily poured into these narrow interstices and completely fill them.

The sulphur or Lavasul is not only readily pourable, but sets to a hard condition which will serve to give good support to the blocks on the drum and will also furnish a good support to the outer edges of the abrasive blocks at the grinding surface of the wheel. The sulphur or Lavasul has good resistance to abrasion, so that the joints at the grinding surface of the wheel will stand up and give continued support to the edges of the abrasive segments.

The use of the sheets of elastic material permit the use of inelastic cementitious filling mainsures terials. In general, the cementitious materials which may be poured in a fluid mobile condition set to a hard inelastic condition and the use of the resilient sheets of fibrous material permits such readily poura'ble cements to be used.

While we have specifically illustrated and described the preferred embodiment of our invention, itis to be understood that the invention is not so limited, but may be otherwise embodied Within the scope of the following claims.

We claim: V

1. A grinding wheel, comprising a metallic body and an abrasive body composed of segmental abrasive blocks and an elastic expansion joint between them comprising a fibrous. sheet and a layer of cementitious material suificiently resilient to permit relative expansion and contraction of the metal relatively to the abrasive body, and means for securing the segmental abrasive blocks to the metallic body.

2. A grinding wheel, comprising segmental blocks and elastic expansion joints between them adapted to yield with the expansion and con= traction of the blocks and thereby prevent rupture of the wheel.

3. A grinding wheel, comprising a drum, seg-' mental abrasive blocks mounted on the drum, means for locking the blocks to the. drum, and expansion joints between the blocks and the drum comprising a layer of paper and a cementitious filling material, said paper being sumciently elastic to permit relative expansionv and contraction of the abrasive or'metal, the locking means relieving the paper from transmitting the strains of grinding from the drum to the blocks.

l. A grinding wheel comprising an abrasive portion and a metallic portion having means for holding the abrasive portion against centrifugal force, and composite expansion joints between the abrasive portion and said holding means and coextensive with the adjacent faces thereof convprising a layer of elastic material and a cementitious filling material.

5. A grinding wheel comprising a drum and segmental blocks mounted thereon about the pe- T riphery thereof, the drum having dove-tailed locking keys engaging undercut recesses m the abrasive, and expansion jointsbetween the look ing keys and the abrasive comprising a layer at water-prooied elastic fibrous material and a cs mentitious material.

6. A grinding wheel comprising a metallic drum, a surrounding body of segmental abrasive seg= ments mounted on the drum, metallic means the drum for holding the abrasive segments against centrifugal movement, and composite ex pansion joints between the abrasive and metal formed of sheets of fibrous material and cementi= tious filling material.

7. A grinding wheel comprising segmental blocks and expansion joints operably disposed be tween the blocks for relieving-the structure of strains set up by varied thermal conditions, said joints comprising elastic material and filling material.

8. A grinding wheel comprising segmental blocks, and expansion joints between the blocks so disposed as to be subject to and relieve strains in the wheel structure by reason of varying ther= mal conditions, said joints comprising a layer of elastic material, and a layer of cement, the elastic material being impervious to the cement.

9. A grinding wheel comprising a composite body formed of a metallic element and a plurality of bonded abrasive elements, and expansion joints till memos giving support to the stone throughout the area of its bore and edepted to surround the driving member, said core having 9, different eoemcient of eizpension from that of the stone. means for holding the seentei abrasive blocks on the core, onol annular means intermediate said core end stone oi e form and materiel to compensate for the olifierences in the eoeifieients of expansion of the stone end oore. 

